Alderkamp Anne-Carlijn, Kulk Gemma, Buma Anita G J, Visser Ronald J W, Van Dijken Gert L, Mills Matthew M, Arrigo Kevin R
Department of Ocean Ecosystems, Energy and Sustainability Research Institute, University of Groningen, Nijenborgh 7, 9747 AG, Groningen, The Netherlands Department of Environmental Earth System Science, Stanford University, Stanford, California 94305, USADepartment of Ocean Ecosystems, Energy and Sustainability Research Institute, University of Groningen, Nijenborgh 7, 9747 AG, Groningen, The NetherlandsDepartment of Environmental Earth System Science, Stanford University, Stanford, California 94305, USA.
J Phycol. 2012 Feb;48(1):45-59. doi: 10.1111/j.1529-8817.2011.01098.x. Epub 2012 Jan 6.
The effects of iron limitation on photoacclimation to dynamic irradiance were studied in Phaeocystis antarctica G. Karst. and Fragilariopsis cylindrus (Grunow) W. Krieg. in terms of growth rate, photosynthetic parameters, pigment composition, and fluorescence characteristics. Under dynamic light conditions mimicking vertical mixing below the euphotic zone, P. antarctica displayed higher growth rates than F. cylindrus both under iron (Fe)-replete and Fe-limiting conditions. Both species showed xanthophyll de-epoxidation that was accompanied by low levels of nonphotochemical quenching (NPQ) during the irradiance maximum of the light cycle. The potential for NPQ at light levels corresponding to full sunlight was substantial in both species and increased under Fe limitation in F. cylindrus. Although the decline in Fv /Fm under Fe limitation was similar in both species, the accompanying decrease in the maximum rate of photosynthesis and growth rate was much stronger in F. cylindrus. Analysis of the electron transport rates through PSII and on to carbon (C) fixation revealed a large potential for photoprotective cyclic electron transport (CET) in F. cylindrus, particularly under Fe limitation. Probably, CET aided the photoprotection in F. cylindrus, but it also reduced photosynthetic efficiency at higher light intensities. P. antarctica, on the other hand, was able to efficiently use electrons flowing through PSII for C fixation at all light levels, particularly under Fe limitation. Thus, Fe limitation enhanced the photophysiological differences between P. antarctica and diatoms, supporting field observations where P. antarctica is found to dominate deeply mixed water columns, whereas diatoms dominate shallower mixed layers.
在南极棕囊藻（Phaeocystis antarctica G. Karst.）和圆柱脆杆藻（Fragilariopsis cylindrus (Grunow) W. Krieg.）中，研究了铁限制对动态光照适应的影响，涉及生长速率、光合参数、色素组成和荧光特性。在模拟真光层以下垂直混合的动态光照条件下，无论是在铁（Fe）充足还是铁限制条件下，南极棕囊藻的生长速率都高于圆柱脆杆藻。在光周期的光照最强时，两个物种都表现出叶黄素脱环氧化，同时伴随着低水平的非光化学猝灭（NPQ）。在对应于全日照的光照水平下，两个物种的NPQ潜力都很大，并且在圆柱脆杆藻中，铁限制条件下NPQ潜力增加。尽管在铁限制条件下，两个物种的Fv /Fm下降相似，但圆柱脆杆藻中伴随的最大光合速率和生长速率的下降要强得多。对通过光系统II并进入碳（C）固定的电子传输速率的分析表明，圆柱脆杆藻中存在很大的光保护循环电子传输（CET）潜力，特别是在铁限制条件下。可能，CET有助于圆柱脆杆藻的光保护，但它也降低了高光强下的光合效率。另一方面，南极棕囊藻能够在所有光照水平下有效地利用通过光系统II流动的电子进行碳固定，特别是在铁限制条件下。因此，铁限制增强了南极棕囊藻和硅藻之间的光生理差异，这支持了野外观察结果，即在深度混合的水柱中发现南极棕囊藻占主导地位，而硅藻则在较浅的混合层中占主导地位。
